The present invention consists of a unit to heat potable water for domestic consumption or for industrial use using solar energy. The unit can be applied based primarily on natural convection circulation of fluid, called thermo-siphon circulation, although forced circulation is also feasible. This unit is low cost, low maintenance, and has a long useful life. These features, combined with its high efficiency, make it a compact unit that is easy to install by being directly applied to pressurized water pipe networks. The temperatures involved in the described applications include water for potable or recreational home use and for potable industrial use.
The low cost of the units of the present invention is based on efficient utilization of polymeric materials together with high-performance industrial manufacturing processes. Consequently, the circulation of the fluid occurs in a exchanger made of polymeric material. The low maintenance of the units is possible due to the non-stick properties of polymers in general, especially those of the polymer used in the present invention, which in general have a different coefficient of thermal expansion than elements that tend to precipitate and adhere to the exchanger's internal surfaces. This translates to a low tendency to generate sediment and deposit buildup, especially in areas where available water has large amounts of diluted, suspended salts. Finally, a long useful life is achieved through an appropriate design that guarantees the mechanical durability of the exchanger, as well as the durability of the box containing the exchanger and the translucent cover of its side exposed to the sun. The mechanical durability of the exchanger is suitable for high pressure applications, i.e., connection directly to household potable water supply, and industrial potable water and fluid networks. Its mechanical durability includes an adequate capacity to account for freezing of the fluid inside the exchanger, especially when the fluid is water or some similar fluid that increases in volume when freezing, a scenario that is quite likely given that units are located outdoors for their operation.
Currently, in applications for heating water for domestic use, most of the systems that heat water through solar energy that are operated by thermo-siphon are made of rigid materials (copper, aluminum, glass) favoring their ability to transfer solar radiation into the water because of their high heat transfer coefficient over their ability to function correctly when other variables, such as the weather or environment, affect their operation. Among the variables that affect the proper functioning of a unit to heat water using solar energy is the possible freezing of the liquid to the inside of the panel and the generation of rust and deposit buildup from the contact between the water and the metal. Freezing brings about a liquid expansion to the inside of the collector with commensurate material damage, creating leaks in the system. The rust and deposit buildup, along with affecting the potability of the water, create an insulating crust that affects the efficiency of the system, which could block the pipes, preventing fluid recirculation. The described problems oblige the implementation of various systems to avoid malfunction from freezing, among which include:                The use of antifreeze liquids, for which the implementation of a heat exchanger is required to transfer heat from the antifreeze liquid flowing through the unit to the fluid to be used eventually.        Automatic drainage systems, where the panel is emptied when the temperature is equal to or less than 0 degrees Celsius, or the freezing point of the fluid being used.        Forced recirculation system, which re-circulates tank water when its temperature approaches freezing. For this, a pump and a differential thermostat must be installed, increasing the cost, complexity, and the possibility of malfunctioning of the unit to heat fluid through solar energy.        
Regarding the formation of sediment and deposit buildup, state-of-the-art heat exchangers in the units should, after a certain period of operation, have their circuits cleaned thoroughly which requires partial or complete dismantling. This generates high maintenance costs, especially considering that the units usually have to be installed in hard-to-access places such as terraces and roofs.
Regarding state-of-the-art features, various disclosures on exchange units all point to small modifications that deviate from the main goal of this type of unit: to efficiently utilize available solar energy.
A system to connect a series of connecting pipes to a common intake to create a heat exchanger is detailed in document CH621622. The main difference between what is detailed in the cited document and the present invention lies in the composition of the joints of the intake manifold and the parallel connecting pipes. The document details mechanical joints made of three separate elements that allow for the configuration of an exchange circuit. The arrangement of three elements is maintained by mechanical interface, which does not ensure proper functioning when the internal fluid is pressurized due to the risk of leakage. This mechanical interface is based on the elastic strain on components during the assembly. This elastic force can diminish during the life of the joint and the exposure of the material to heat and solar radiation.
The exchanger of the present invention, on the other hand, is obtained by the arrangement of two elements: the manifold and pipes melted together by a thermo-fusion process, which creates a thermoplastic molecular union of the same type and quality as that found in the very material of the constituent parts. With this solution, leaks are eliminated because the interior circuit is one piece, which is able to operate at high pressure, allowing for its direct connection to potable water networks. The detailed framework of the cited document is used in pool collecting applications and in solar-heating circuits whose independent circuits are unpressurized, where operation under pressure is not required. A heat exchanger such as this detailed one has a difficult time withstanding use in freezing temperatures and when connected to pressurized networks, circumstances that frequently occur due to pressures from liquid hammering or pulsations from pumping systems.
Another document regarding state-of-the-art features that discloses details regarding the connection of the intake manifold to the parallel pipes is CA1291474. The detailed elements have a tube coil in whose transverse cutting it is possible to distinguish different rings of material (metal, rubber, and plastic) that allow for various applications, but whose primary one is to exchange heat from a primary source to a secondary source. This approach explains the layout of the pipes, which follows the logic of a radiator's layout, where what is sought is the creation a circuit that is able to distribute heat dissipated by the pipes as evenly as possible, which implies the existence of an impeller pump and a closed circuit. This disclosed closed circuit layout allows for the incorporation of special preventative additives to the fluid for proper functioning through time. This markedly differentiates it from the system of the invention in question, which is designed to forgo the need for a secondary circuit and additional components, allowing for the system to process potable water through its interior and favoring a system configuration that allows for greater solar collection that minimizes energy loss. Additionally, this configuration and the composition of the present invention, with connecting pipes in parallel, allows for the upward running of water inside of it, which in turn allows for thermo-siphoning.
In document GB2445222 an example of a more comprehensive disclosure can be found. In this document, a system is disclosed that allows configuring solar collection covers, without the need to install solar panels as extra elements to a house itself. Modules are made up internally of a series of copper pipes that are welded to copper solar collection propellers. These modules' design thus allows for a greater surface area to capture solar energy and the ability to mount these on roofs of buildings. The cover of these shingles is made of plastic material. This does not allow for thermo-siphoning operation of these modules and requires a secondary circuit that contributes to a heat exchanger, and is commanded by a pump that enables the fluid's movement. To summarize, the product seeks to solve the architectural alterations due to solar panels, betting on spanning a large collection area, rather than efficiently using solar energy in a system. The system of the present invention, on the other hand, is configured to obtain maximum yields, with the simplest system possible, thus avoiding secondary heat exchangers and complex circuits while favoring a simple operating system that can be connected directly to the home network.
Another document regarding state-of-the-art features, mainly focused on construction elements of the box, is DE10321422. In this document the joints of the heat exchanger's receiver box of a type of solar panel are described. The document describes the configuration of an angular piece that enables the mechanical fastening of the box's side panels. Additionally, it describes a superior tab that a second piece fits to to hold together the translucent cover through pressure. The box described in the cited document follows a rigid framework design for the configuration of a solar panel in its interior. The model developed in the present invention poses a box that will allow for the best performance of the solar collector inside the box, i.e., the box is an integral part of the solar collector's design in order to achieve optimum collection and functioning of the operation features described in the preceding paragraphs.
All the documents described deviate from the main purpose of the present invention, and they do not achieve its features, i.e., being low cost, low maintenance, and having a long useful life. These features, combined with its high efficiency, allow for compact units that are easy to install directly to pressurized potable water networks.
From the perspective that the best features in industrial or domestic water circuits are obtained when the prime qualities of the panel are capitalized on, prime application occurs when the panel is used connected to the working pressure of the water of fluid network that one desires to heat, using thermo-siphon convection circulation, or should that fail if an isolated recirculation tank on the panel is not possible, forced circulation towards an isolated recirculation tank connected directly to the network, but located in an arbitrary place, is used.